1. Field of the Invention
The present invention relates to a method for etching a feature in a substrate, and more particularly to a method for etching a feature in a substrate using a multi-layer mask.
2. Description of Related Art
Typically, during fabrication of integrated circuits (ICs), semiconductor production equipment utilize a (dry) plasma etch process to remove or etch material along fine lines or within vias or contacts patterned on a semiconductor substrate. The success of the plasma etch process requires that the etch chemistry includes chemical reactants suitable for selectively etching one material while substantially not etching another material. For example, on a semiconductor substrate, a pattern formed in a protective layer can be transferred to an underlying layer of a selected material utilizing a plasma etching process. The protective layer can comprise a light-sensitive layer, such as a photoresist layer, having a pattern formed using a lithographic process. Once the pattern is formed, the semiconductor substrate is disposed within a plasma processing chamber, and an etching chemistry is formed that selectively etches the underlying layer while minimally etching the protective layer. This etch chemistry is produced by introducing an ionizable, dissociative gas mixture having parent molecules comprising molecular constituents capable of reacting with the underlying layer while minimally reacting with the protective layer. The production of the etch chemistry comprises introduction of the gas mixture and formation of plasma when a portion of the gas species present are ionized following a collision with an energetic electron. Moreover, the heated electrons serve to dissociate some species of the gas mixture and create a reactive mixture of chemical constituents (of the parent molecules). Thereafter, the ionized gas species and reactive mixture of chemical constituents facilitate the etching of various features (e.g., trenches, vias, contacts, etc.) in the exposed regions of substrate. Such substrate materials where etching is required include silicon dioxide (SiO2), low dielectric constant (low-k) materials, ultra-low-k materials, polycrystalline silicon, silicon and silicon nitride, for example.